This invention relates generally to image processing. More particularly, it relates to an improved method for performing image enhancement processing on a portion of an image without leaving a cut-out appearance on the enhanced image.
In image processing, frequently an image will be too dark, too red, too green or have some other defect which will require an image processing operation to be uniformly applied over the entire image. Also frequently, however, only one portion of the image will require a particular image processing effect. For example, a user, or shall we say an artist, might want to increase the red in the center of a portrait to enhance the skin tones, but leave the edges or background untouched. To alter only one portion of an image with an effect, it is known to define a mask area to block a portion of the image from by the chosen image processing operation.
Heretofore, the known imaging applications and devices have shared one or both of the following defects for masked imaging operations: A significant delay between the time the user has input the type and extent of the desired imaging effect and/or a sharp line separating the masked and unmasked areas of the image.
First, color enhancement in image processing is inherently a "right brained", creative activity. That is, the decision that more red is required in a specific area of an image is an aesthetic and artistic decision. Yet image processing with a data processing system relies on numeric quantization of the effect, forcing the artist into a left-brained approach to achieve the desired changes. Image systems ask the artist to express desires as "fifty percent magenta" or "ten percent more contrast". Changing an image according to numerical calculations is hardly intuitive to a user and makes it difficult to optimize the image. This is particularly true if the user is inexperienced. Compounding this problem, is that many image processing systems require a long delay while the processor calculates how to display the result of the image processing effect on the image.
An expert able to work effectively with the delayed system has through experience constructed a mental model which gives instantaneous mental feedback. Such an expert can visualize what more magenta will do to a picture before going into a darkroom. However, such a model requires training and limits the number of variables the artist can handle. Even then, multiple iterations are often required for accuracy. For a non-expert who has not developed this mental model, useful image processing color enhancement can only be done with instantaneous feedback. Instantaneous feedback makes everyone an instant expert and adds excitement and immediacy to the process.
Second, many image processing systems which use a masking effect leave a sharp line between the area where the image processing effect was carried out and that area which was masked. This is unacceptable as most edges in an image are surprisingly diffused under magnification. To avoid a cut-out appearance around the changed area, the mask must have a fuzzy or diffused edge.
To make an image enhancement program for the widest possible market, it must combine a fuzzy mask with instantaneous feedback for the imaging effect. The prior art could give only one or the other. This invention improves an image processing operation carried out on a masked image by both providing instantaneous feedback to the user and eliminating the cut-out appearance of the enhanced image.